Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS5683615 A
Publication typeGrant
Application numberUS 08/664,035
Publication date4 Nov 1997
Filing date13 Jun 1996
Priority date13 Jun 1996
Fee statusPaid
Also published asCA2257952A1, DE69731833D1, EP0904592A1, EP0904592B1, WO1997048110A1
Publication number08664035, 664035, US 5683615 A, US 5683615A, US-A-5683615, US5683615 A, US5683615A
InventorsBeth C. Munoz
Original AssigneeLord Corporation
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Magnetorheological fluid
US 5683615 A
Abstract
A magnetorheological fluid that includes magnetic-responsive particles, a carrier fluid and at least one thiophosphorus and/or thiocarbamate additive. Preferably, the thiophosphorus or thiocarbamate additive is a metallic dialkyldithiophosphate or a metallic dialkyldithiocarbamate.
Images(8)
Previous page
Next page
Claims(44)
What is claimed is:
1. A magnetorheological fluid comprising magnetic-responsive particles, a carrier fluid and at least one thiophosphorus additive having a structure represented by: ##STR4## wherein R3 is selected from the group consisting of a metallic ion, a non-metallic moiety and a divalent moiety; a and b are each individually 0 or 1, provided a+b is at least equal to 1; x is an integer from 1 to 5 depending upon the valence number of R3 ; and R1 and R2 each individually have a structure represented by
Y--((C)(R4)(R5))n --(O)w --
wherein Y is selected from the group consisting of hydrogen, amino, amido, imido, carboxyl, hydroxyl, carbonyl, oxo and aryl;
n is an integer from 2 to 17;
R4 and R5 can each individually be hydrogen, alkyl or alkoxy; and
w is 0 or 1.
2. A magnetorheological fluid according to claim 1, wherein a is 1 and b is 1.
3. A magnetorheological fluid according to claim 1, wherein R1 and R2 are alkyl or alkoxy groups.
4. A magnetorheological fluid according to claim 1, wherein R3 comprises a metallic ion selected from the group consisting of molybdenum, tin, antimony, lead, bismuth, nickel, iron, zinc, silver, cadmium and lead.
5. A magnetorheological fluid according to claim 4, wherein R3 comprises an ionic group selected from the group consisting of a carbide, an oxide, a sulfide and an oxysulfide of molybdenum, tin, antimony, lead, bismuth, nickel, iron, zinc, silver, cadmium or lead.
6. A magnetorheological fluid according to claim 4, wherein R3 comprises a metallic ion selected from the group consisting of antimony, zinc, cadmium, nickel and molybdenum.
7. A magnetorheological fluid according to claim 1, wherein R3 comprises a non-metallic moiety selected from the group consisting of hydrogen, alkyl, alkylaryl, arylalkyl, hydroxyalkyl, oxy-containing group, amido and amino.
8. A magnetorheological fluid according to claim 1, wherein the thiophosphorus additive comprises a dimer wherein R3 comprises an alkylene and x is 2.
9. A magnetorheological fluid according to claim 1, wherein the thiophosphorus additive is selected from the group consisting of sulfurized oxymolybdenum organophosphorodithioate, antimony dialkylphosphorodithioate and molybdenum dialkylphosphorodithioate.
10. A magnetorheological fluid according to claim 1, wherein the thiophosphorus additive is present in an amount of 0.1 to 12 percent by volume, based on the volume of the magnetorheological fluid.
11. A magnetorheological fluid according to claim 1, further comprising at least one additional additive selected from the group consisting of an organomolybdenum, a phosphate, a sulfur-containing compound, and a thiocarbamate having a structure represented by the formula: ##STR5## wherein R3 is selected from the group consisting of a metallic ion, a non-metallic moiety and a divalent moiety; a and b are each individually 0 or 1, provided a+b is at least equal to 1; x is an integer from 1 to 5 depending upon the valence number of R3 ; and R1 and R2 each individually have a structure represented by
Y--((C)(R4)(R5))n --
wherein Y is selected from the group consisting of hydrogen, amino, amido, imido, carboxyl, hydroxyl, carbonyl, oxo and aryl;
n is an integer from 2 to 17; and
R4 and R5 can each individually be hydrogen, alkyl or alkoxy.
12. A magnetorheological fluid according to claim 11, wherein the additional additive is present in an amount of 0.1 to 12 percent by volume, based on the volume of the magnetorheological fluid.
13. A magnetorheological fluid according to claim 1, wherein the magnetic-responsive particles have an average particle size of 0.1 to 500 μm.
14. A magnetorheological fluid according to claim 1, wherein the magnetic-responsive particles have an average particle size of at least 1 μm.
15. A magnetorheological fluid according to claim 1, wherein the carrier fluid comprises at least one fluid selected from the group consisting of natural fatty oil, mineral oil, polyphenylether, dibasic acid ester, neopentylpolyol ester, phosphate ester, polyester, cycloparaffin oil, paraffin oil, unsaturated hydrocarbon oil, synthetic hydrocarbon oil, monobasic acid ester, glycol ester, glycol ether, perfluorinated polyether and halogenated hydrocarbon.
16. A magnetorheological fluid according to claim 15, wherein the carrier fluid is selected from the group consisting of mineral oil, paraffin oil, cycloparaffin oil, and synthetic hydrocarbon oil.
17. A magnetorheological fluid according to claim 16, wherein the carrier fluid comprises a synthetic hydrocarbon oil derived from poly-α-olefin.
18. A magnetorheological fluid according to claim 1 wherein the carrier fluid comprises a fluid that is substantially non-volatile, non-polar and non-aqueous.
19. A magnetorheological fluid according to claim 1, wherein the magnetic-responsive particles have an average particle size of 0.1 to 500 μm and the carrier fluid is selected from the group consisting of mineral oil, paraffin oil, cycloparaffin oil, and synthetic hydrocarbon oil.
20. A magnetorheological fluid comprising magnetic-responsive particles, a carrier fluid and at least one thiocarbamate additive having a structure represented by: ##STR6## wherein R3 is selected from the group consisting of a metallic ion, a non-metallic moiety and a divalent moiety; a and b are each individually 0 or 1, provided a+b is at least equal to 1; x is an integer from 1 to 5 depending upon the valence number of R3 ; and R1 and R2 each individually have a structure represented by
Y--((C)(R4)(R5))n --
wherein Y is selected from the group consisting of hydrogen, amino, amido, imido, carboxyl, hydroxyl, carbonyl, oxo and aryl;
n is an integer from 2 to 17; and
R4 and R5 can each individually be hydrogen, alkyl or alkoxy.
21. A magnetorheological fluid according to claim 20, wherein a is equal to 1 and b is equal to 1.
22. A magnetorheological fluid according to claim 20, wherein R1 and R2 are alkyl.
23. A magnetorheological fluid according to claim 20, wherein R3 comprises a metallic ion selected from the group consisting of molybdenum, tin, antimony, lead, bismuth, nickel, iron, zinc, silver, cadmium and lead.
24. A magnetorheological fluid according to claim 23, wherein R3 comprises an ionic group selected from the group consisting of a carbide, an oxide, a sulfide and an oxysulfide of molybdenum, tin, antimony, lead, bismuth, nickel, iron, zinc, silver, cadmium or lead.
25. A magnetorheological fluid according to claim 23, wherein R3 comprises a metallic ion selected from the group consisting of antimony, zinc, cadmium, nickel and molybdenum.
26. A magnetorheological fluid according to claim 20, wherein R3 comprises a non-metallic moiety selected from the group consisting of hydrogen, alkyl, alkylaryl, arylalkyl, hydroxyalkyl, oxy-containing group, amido and amino.
27. A magnetorheological fluid according to claim 20, wherein the thiocarbamate additive comprises a dimer wherein R3 comprises an alkylene and x is 2.
28. A magnetorheological fluid according to claim 20, wherein the thiocarbamate additive is selected from the group consisting of molybdenum oxysulfide dithiocarbamate, organo molybdenum dithiocarbamate, zinc diamyldithiocarbamate, lead diamyldithiocarbamate and antimony dialkyldithiocarbamate.
29. A magnetorheological fluid according to claim 20, wherein the thiocarbamate additive is present in an amount of 0.1 to 12 percent by volume, based on the volume of the magnetorheological fluid.
30. A magnetorheological fluid according to claim 20, further comprising at least one additional additive selected from the group consisting of an organomolybdenum, a phosphate and a sulfur-containing compound.
31. A magnetorheological fluid according to claim 30, wherein the additional additive is present in an amount of 0.1 to 12 percent by volume, based on the volume of the magnetorheological fluid.
32. A magnetorheological fluid according to claim 20, wherein the magnetic-responsive particles have an average particle size of 0.1 to 500 μm.
33. A magnetorheological fluid according to claim 20, wherein the magnetic-responsive particles have an average particle size of at least 1 μm.
34. A magnetorheological fluid according to claim 20, wherein the carrier fluid comprises at least one fluid selected from the group consisting of natural fatty oil, mineral oil, polyphenylether, dibasic acid ester, neopentylpolyol ester, phosphate ester, polyester, cycloparaffin oil, paraffin oil, unsaturated hydrocarbon oil, synthetic hydrocarbon oil, monobasic acid ester, glycol ester, glycol ether, synthetic hydrocarbon oil, perfluorinated polyether and halogenated hydrocarbon.
35. A magnetorheological fluid according to claim 34, wherein the carrier fluid is selected from the group consisting of mineral oil, paraffin oil, cycloparaffin oil, and synthetic hydrocarbon oil.
36. A magnetorheological fluid according to claim 35, wherein the carrier fluid comprises a synthetic hydrocarbon oil derived from polyalphaolefin.
37. A magnetorheological fluid according to claim 20, wherein the carrier fluid comprises a fluid that is substantially non-volatile, non-polar and non-aqueous.
38. A magnetorheological fluid according to claim 20 wherein the magnetic-responsive particles have an average particle size of 0.1 to 500 μm and the carrier fluid is selected from the group consisting of mineral oil, paraffin oil, cycloparaffin oil, and synthetic hydrocarbon oil.
39. A magnetorheological fluid according to claim 1 wherein the thiophosphorus additive comprises a metallic dialkyldithiophosphate.
40. A magnetorheological fluid according to claim 20 wherein the thiocarbamate additive comprises a metallic dialkyldithiocarbamate.
41. A magnetorheological fluid according to claim 1 further comprising a carboxylate soap.
42. A magnetorheological fluid according to claim 41 wherein the carboxylate soap is selected from the group consisting of lithium stearate, calcium stearate, aluminum stearate, ferrous oleate, ferrous naphthenate, zinc stearate, sodium stearate and strontium stearate.
43. A magnetorheological fluid according to claim 20 further comprising a carboxylate soap.
44. A magnetorheological fluid according to claim 43 wherein the carboxylate soap is selected from the group consisting of lithium stearate, calcium stearate, aluminum stearate, ferrous oleate, ferrous naphthenate, zinc stearate, sodium stearate and strontium stearate.
Description
BACKGROUND OF THE INVENTION

This invention relates to fluids that exhibit substantial increases in flow resistance when exposed to magnetic fields.

Fluid compositions that undergo a change in apparent viscosity in the presence of a magnetic field are commonly referred to as Bingham magnetic fluids or magnetorheological fluids. Magnetorheological fluids typically include magnetic-responsive particles dispersed or suspended in a carrier fluid. In the presence of a magnetic field, the magnetic-responsive particles become polarized and are thereby organized into chains of particles or particle fibrils within the carrier fluid. The chains of particles act to increase the apparent viscosity or flow resistance of the overall materials resulting in the development of a solid mass having a yield stress that must be exceeded to induce onset of flow of the magnetorheological fluid. The force required to exceed the yield stress is referred to as the "yield strength". In the absence of a magnetic field, the particles return to an unorganized or free state and the apparent viscosity or flow resistance of the overall materials is correspondingly reduced. Such absence of a magnetic field is referred to herein as the "off-state".

Magnetorheological fluids are useful in devices or systems for controlling vibration and/or noise. For example, magnetorheological fluids are useful in providing controllable forces acting upon a piston in linear devices such as dampers, mounts and similar devices. Magnetorheological fluids are also useful for providing controllable torque acting upon a rotary in rotary devices. Possible linear or rotary devices could be clutches, brakes, valves, dampers, mounts and similar devices. In these applications magnetorheological fluid can be subjected to shear forces, as high as 70 kPa, often significantly high, and shear rates in the order of 20,000 to 50,000 sec-1 causing extreme wear on the magnetic-responsive particles. As a result, the magnetorheological fluid thickens substantially over time leading to increasing off-state viscosity. The increasing off-state viscosity leads to an increase in off-state force experienced by the piston or rotor. This increase in off-state force hampers the freedom of movement of the piston or rotor at off-state conditions. In addition, it is desirable to maximize the ratio of on-state force to off-state force in order to maximize the controllability offered by the device. Since the on-state force is dependent upon the magnitude of the applied magnetic field, the on-state force should remain constant at any given applied magnetic field. If the off-state force increases over time because the off-state viscosity is increasing but the on-state force remains constant, the on-state/off-state ratio will decrease. This on-state/off-state ratio decrease results in undesirable minimization of the controllability offered by the device. A more durable magnetorheological fluid that does not thicken over an extended period of time, preferably over the life of the device that includes the fluid, would be very useful.

Magnetorheological fluids are described, for example, in U.S. Pat. No. 5,382,373 and published PCT International Patent Applications WO 94/10692, WO 94/10693 and WO 94/10694.

U.S. Pat. No. 5,271,858 relates to an electrorheological fluid that includes a carbon, glass, silicate, or ceramic particulate having an electrically conductive tin dioxide coating. The patent provides an extensive list of possible carrier fluids for the electrorheological fluid that includes esters and amides of an acid of phosphorus, hydrocarbon materials, silicates, silicones, ether compounds, polyphenyl thioether compounds, phenylmercaptobiphenyl compounds, mono- and di alkylthiophenes, chlorinated compounds and esters of polyhydric compounds.

U.S. Pat. No. 5,043,070 relates to an organic solvent extractant that includes an organic solvent extractant and magnetic particles, wherein the surface of the magnetic particles has been coated with a surfactant that renders the particles hydrophobic. The surfactant may be selected from ethers, alcohols, carboxylates, xanthates, dithiophosphates, phosphates, hydroxamates, sulfonates, sulphosuccinates, taurates, sulfates, amino acids or amines. Sodium dialkyl dithiophosphate and aryl dithiophosphoric acid are the only dithiophosphates mentioned in the extensive list of possible surfactants. There is no example, however, that includes a dithiophosphate.

U.S. Pat. No. 4,834,898 relates to an extracting reagent for magnetizing particles of nonmagnetic material that comprises water that includes magnetic particles having a 2 layer surfactant coating. The surfactant layers may be selected from ethers, alcohols, carboxylates, xanthates, dithiophosphates, phosphates, hydroxamates, sulfonates, sulphosuccinates, taurates, sulfates, amino acids or amines.

U.S. Pat. No. 4,253,886 relates to a method for preparing a ferromagnetic metal powder of particle size from 50-1000 angstroms. The particles are washed with a solution that contains (a) a volatile corrosion inhibitor; (b) (i) water, (ii) a water miscible organic solvent or (iii) a combination of (i) and (ii); and (c) an anionic surface active agent. Salt of a dithiophosphoric acid ester is mentioned as one of many possible types of surface active agents.

JP-B-89021202 relates to a magnetic powder that is iron or mainly iron that is surface treated with dialkyl dithiocarbamates of formula R1 R2 N--CS--S--R3 wherein R1 and R2 are alkyl and R3 is alkali metal or ammonium. The powder is used to formulate magnetic ink by mixing it with methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, vinylchloride/vinyl acetate copolymer, polyurethane resin, stearic acid, lecithin and a curing agent.

JP-A-62195729 relates to a magnetic lacquer for coating onto a substrate to make a recording medium. According to an English language abstract an example of the lacquer includes 100 parts by weight (pbw) Co-containing γ-Fe2 O3, 4 pbw α-Fe2 O3 powder, 4 pbw Mo-dithiocarbamate, 12 pbw nitrocellulose, 8 pbw polyurethane resin, 75 pbw cyclohexanone, 75 pbw toluene, 7.5 pbw methyl isobutyl ketone and 5 pbw polyisocyanate.

DD-A-296574 relates to a magnetic liquid that may includes magnetite monodomain particles with particle sizes of 5-20 nm. Zn dialkyldithiophosphide is included as a component at some stage in the production of the fluid, but it is not clear from an English language abstract what other components are present in a fluid with the Zn dialkyldithiophosphide.

None of these documents suggest any solution to the problem of providing a more durable magnetorheological fluid.

SUMMARY OF THE INVENTION

According to a first embodiment of the invention there is provided a magnetorheological fluid that includes magnetic-responsive particles, a carrier fluid and at least one thiophosphorus additive having a structure represented by formula A: ##STR1## wherein R1 and R2 each individually have a structure represented by:

Y--((C)(R4)(R5))n --(O)w --

wherein Y is hydrogen or a functional group--containing moiety such as an amino, amido, imido, carboxyl, hydroxyl, carbonyl, oxo or aryl;

n is an integer from 2 to 17 such that C(R4)(R5) is a divalent group having a structure such as a straight-chained aliphatic, branched aliphatic, heterocyclic, or aromatic ring;

R4 and R5 can each individually be hydrogen, alkyl or alkoxy; and

w is 0 or 1.

According to a second embodiment of the invention them is provided a magnetorheological fluid that includes magnetic-responsive particles, a carrier fluid and at least one thiocarbamate additive having a structure represented by formula B: ##STR2## wherein R1 and R2 each individually have a structure represented by:

Y--((C)(R4)(R5))n --

wherein Y is hydrogen or a functional group--containing moiety such as an amino, amido, imido, carboxyl, hydroxyl, carbonyl, oxo or aryl;

n is an integer from 2 to 17 such that C(R4)(R5) is a divalent group having a structure such as a straight-chained aliphatic, branched aliphatic, heterocyclic, or aromatic ring; and

R4 and R5 can each individually be hydrogen, alkyl or alkoxy.

R3 of formula A or B can be a metal ion such as molybdenum, tin, antimony, lead, bismuth, nickel, iron, zinc, silver, cadmium or lead or a nonmetallic moiety such as hydrogen, a sulfur-containing group, alkyl, alkylaryl, arylalkyl, hydroxyalkyl, an oxy-containing group, amido or an amine. Subscripts a and b of formula A or B are each individually 0 or 1, provided a+b is at least equal to 1 and x of formula A or B is an integer from 1 to 5 depending upon the valence number of R3.

The magnetorheological fluids of the invention exhibit superior durability because of a substantial decrease in the thickening of the fluid over a period of use.

There also is provided according to the invention a magnetorheological device that includes a housing that contains the above-described magnetorheological fluids.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

R1 and R2 of the thiophosphorus or thiocarbamate additive can be any group that imparts solubility with the carrier fluid. R1 and R2 preferably individually have the structure depicted previously for the thiophosphorus and thiocarbamate additives, respectively.

One possibility for R1 and/or R2 for both the thiophosphorus and thiocarbamate is an alkyl group. In general, any alkyl group should be suitable, but alkyls having from 2 to 17, particularly 3 to 16, carbon atoms are preferred. The alkyl could be branched if R4 and/or R5 are themselves alkyls or the alkyl could be straight-chained. Illustrative alkyl groups include methyl, ethyl, propyl, isopropyl, tert-butyl, pentyl, 2-ethylhexyl, dodecyl, decyl, hexadecyl, nonyl, octodecyl, and 2-methyl dodecyl.

Another possibility for R1 and/or R2 for both the thiophosphorus and thiocarbamate is an aryl group. In general, any aryl groups should be suitable. The aryl group can be directly bonded to the phosphorus atom of the thiophosphorus or it can be bonded via a divalent linking group such as an alkylene or an amido group. The aryl group can be bonded to the nitrogen atom of the of the thiocarbamate via a divalent linking group such as an alkylene or an amido group. Illustrative aryl-containing groups include phenyl, benzoyl and naphthyl. In general, any alkylaryl groups should be suitable. Illustrative alkylaryl groups include benzyl, phenylethyl, phenylpropyl and alkyl-substituted phenyl alcohol.

A further possibility for R1 and/or R2 for the thiophosphorus is an alkoxy group (in other words, subscript w is 1). In general, any alkoxy should be suitable, but alkoxy groups having from 2 to 17, preferably 3 to 16, carbon atoms are preferred. Illustrative alkoxy groups include methoxy, ethoxy, propoxy, and butoxy.

If Y is an amino group, possible R1 and/or R2 groups for the thiophosphorus and thiocarbamate include butylamine, nonylamine, hexadecylamine and decylamine. If Y is an amido group, possible R1 and/or R2 groups include butynoamido, decynoamido, pentylamido and hexamido. If Y is a hydroxy group, possible R1 and/or R2 groups include decanol, hexanol, pentanol, and alkyl groups that include a hydroxy anywhere along the chain such as, for example, 4-decanol. If Y is a carbonyl or oxo group, possible R1 and/or R2 groups include 2-decanone, 3-decanone, 4-decanone, 2-pentanone, 3-pentanone, 4-pentanone and decanophenone. Y could also be a combination of the above-described functional groups so that R1 or R2 could be a multi-functional moiety such as benzamido.

As described above, R4 and R5 can be hydrogen, alkyl or alkoxy. For example, if R1 or R2 is an aryl or straight-chained alkyl, R4 and R5 are hydrogen. If R1 or R2 is a substituted aryl or a branched alkyl, R4 and R5 are alkyl or alkoxy. The number of carbons in the alkyl or alkoxy for R4 and R5 can vary, but the preferred range is 1 to 16, more preferably 1 to 10.

Preferred groups for R1 and R2 of formula A (the thiophosphorus) are decyl, octyl, nonyl, dodecyl, hexadecyl, undecyl, hexyl, butoxy, pentoxy, decoxy and hexaoxy. Preferred groups for R1 and R2 of formula B (the thiocarbamate) are decyl, octyl, nonyl, dodecyl, hexadecyl, undecyl and hexyl.

R3 of either the thiophosphorus or thiocarbamate additive can be a metallic ion such as molybdenum, tin, antimony, lead, bismuth, nickel, iron, zinc, silver, cadmium or lead and the carbides, oxides, sulfides or oxysulfides thereof. Preferably, R3 is antimony, zinc, cadmium, nickel or molybdenum.

R3 also can be a nonmetallic moiety such as hydrogen, alkyl, alkylaryl, arylalkyl, hydroxyalkyl, oxy-containing group, amido or amino. The alkyl, aryl, alkylaryl, arylalkyl, hydroxyalkyl, or oxy-containing groups could include functional groups such as amino, amido, carboxy or carbonyl.

In general, any alkyl group should be suitable, but alkyls having from 2 to 20, preferably 3 to 16, carbon atoms are preferred. The alkyls could be straight chain or branched. Illustrative alkyl groups include methyl, ethyl, propyl, isopropyl, tert-butyl, pentyl, 2-ethylhexyl, dodecyl, decyl, hexadecyl and octadecyl. In general, any aryl groups should be suitable. Illustrative aryl groups include phenyl, benzylidene, benzoyl and naphthyl. In general, any amido-containing groups should be suitable. Illustrative amido groups include butynoamido, decynoamido, pentylamido and hexamido. In general, any amino groups should be suitable. Illustrative amino groups include butylamine, nonylamine, hexadecylamine and decylamine. In general, any alkylaryl or arylalkyl groups should be suitable. Illustrative alkylaryl or arylalkyls include benzyl, phenylethyl, phenylpropyl, and alkyl-substituted phenyl alcohol. In general, any oxy-containing groups should be suitable, but alkoxy groups having from 2 to 20, preferably 3 to 12, carbon atoms are preferred. Illustrative alkoxy groups include methoxy, ethoxy, propoxy, butoxy and heptoxy.

R3 also can be a divalent group that links together two thiophosphorus or thiocarbamates units to form a dimer. In this instance, subscript x of formula A or B will be 2 and the thiocarbamate additive, for example, will have the following formula: ##STR3##

Possible divalent groups include alkylene. In general, any alkylene groups should be suitable, but those having from 1 to 16, preferably 1 to 8, carbon atoms are preferred. Illustrative alkylene groups include methylene and propylene. A commercially available example of an alkylene thiocarbamate is methylene bis(dibutyldithiocarbamate) available from R. T. Vanderbilt Co. under the tradename Vanlube® 7723.

Subscripts a and b of formulae A or B preferably are both 1. In other words, a dithiophosphorus or ditihocarbamate is the preferred additive.

Particularly preferred dithiophosphorus additives include sulfurized oxymolybdenum organophosphorodithioate available from R. T. Vanderbilt Co. under the tradename Molyvan® L, and antimony dialkylphosphorodithioates available from R. T. Vanderbilt Co. under the tradenames Vanlube® 622 and 648. Particularly preferred dithiocarbamates include molybdenum oxysulfide dithiocarbamate available from R. T. Vanderbilt Co. under the tradename Molyvan® A, organo molybdenum dithiocarbamate available from R. T. Vanderbilt Co. under the tradename Molyvan® 822, zinc diamyldithiocarbamate available from R. T. Vanderbilt Co. under the tradename Molyvan® AZ, lead diamyldithiocarbamate available from R. T. Vanderbilt Co. under the tradename Vanlube® 71, and antimony dialkyldithiocarbamate available from R. T. Vanderbilt Co. under the tradename Vanlube® 73.

The thiophosphorus or thiocarbamate additive that is added to the magnetorheological fluid preferably is in a liquid state at ambient room temperature and does not contain any particles above molecular size.

A mixture of a thiophosphorus additive and a thiocarbamate additive could also be used in a magnetorheological fluid. The thiophosphorus and/or thiocarbamate can be present in an amount of 0.1 to 12, preferably 0.25 to 10, volume percent, based on the total volume of the magnetorheological fluid.

It has also been surprisingly found that an advantageous synergistic effect can be achieved if other additives are included with the thiophosphorus and/or thiocarbamate. Examples of such supplemental or second additives include organomolybdenums, phosphates and sulfur-containing compounds.

The organomolybdenum additive can be a compound or complex whose structure includes at least one molybdenum atom bonded to or coordinated with at least one organic moiety. The organic moiety can be, for example, derived from a saturated or unsaturated hydrocarbon such as alkane, or cycloalkane; an aromatic hydrocarbon such as phenol or thiophenol; an oxygen-containing compound such as carboxylic acid or anhydride, ester, ether, keto or alcohol; a nitrogen-containing compound such as amidine, amine or imine; or a compound containing more than one functional group such as thiocarboxylic acid, imidic acid, thiol, amide, imide, alkoxy or hydroxy amine, and amino-thiol-alcohol. The precursor for the organic moiety can be a monomeric compound, an oligomer or polymer. A heteroatom such as ═O, --S or .tbd.N also can be bonded to or coordinated with the molybdenum atom in addition to the organic moiety.

A particularly preferred group of organomolybdenums is described in U.S. Pat. No. 4,889,647 and U.S. Pat. No. 5,412,130, both incorporated herein by reference. U.S. Pat. No. 4,889,647 describes an organomolybdenum complex that is prepared by reacting a fatty oil, diethanolamine and a molybdenum source. U.S. Pat. No. 5,412,130 describes heterocyclic organomolybdates that are prepared by reacting diol, diamino-thiol-alcohol and amino-alcohol compounds with a molybdenum source in the presence of a phase transfer agent. An organomolybdenum that is prepared according to U.S. Pat. No. 4,889,647 and U.S. Pat. No. 5,412,130 is available from R. T. Vanderbilt Co. under the tradename Molyvan® 855.

Organomolybdenums that also might be useful are described in U.S. Pat. No. 5,137,647 which describes an organomolybdenum that is prepared by reacting an amine-amide with a molybdenum source, U.S. Pat. No. 4,990,271 which describes a molybdenum hexacarbonyl dixanthogen, U.S. Pat. No. 4,164,473 which describes an organomolybdenum that is prepared by reacting a hydrocarbyl substituted hydroxy alkylated amine with a molybdenum source, and U.S. Pat. No. 2,805,997 which describes alkyl esters of molybdic acid.

The organomolybdenum additive that is added to the magnetorheological fluid preferably is in a liquid state at ambient room temperature and does not contain any particles above molecular size.

The organomolybdenum additive can be present in an amount of 0.1 to 12, preferably 0.25 to 10, volume percent, based on the total volume of the magnetorheological fluid.

Useful phosphates include alkyl, aryl, alkylaryl, arylalkyl, amine and alkyl amine phosphates. Illustrative of such phosphates are tricresyl phosphate, trixylenyl phosphate, dilauryl phosphate, octadecyl phosphate, hexadecyl phosphate, dodecyl phosphate and didodecyl phosphate. A particularly preferred alkyl amine phosphate is available from R. T. Vanderbilt Company under the tradename Vanlube® 9123. Examples of sulfur-containing compounds include thioesters such as tetrakis thioglycolate, tetrakis(3-mercaptopropionyl) pentaerithritol, ethylene glycoldimercaptoacetate, 1,2,6-hexanetriol trithioglycolate, trimethylol ethane tri(3-mercaptopropionate), glycoldimercaptopropionate, bisthioglycolate, trimethylolethane trithioglycolate, trimethylolpropane tris(3-mercaptopropionate) and similar compounds and thiols such as 1-dodecylthiol, 1-decanethiol, 1-methyl-1-decanethiol, 2-methyl-2-decanethiol, 1-hexadecylthiol, 2-propyl-2-decanethiol, 1-butylthiol, 2-hexadecylthiol and similar compounds.

The magnetic-responsive particle component of the magnetorheological material of the invention can be comprised of essentially any solid which is known to exhibit magnetorheological activity. Typical magnetic-responsive particle components useful in the present invention are comprised of, for example, paramagnetic, superparamagnetic or ferromagnetic compounds. Superparamagnetic compounds are especially preferred. Specific examples of magnetic-responsive particle components include particles comprised of materials such as iron, iron oxide, iron nitride, iron carbide, carbonyl iron, chromium dioxide, low carbon steel, silicon steel, nickel, cobalt, and mixtures thereof. The iron oxide includes all known pure iron oxides, such as Fe2 O3 and Fe3 O4, as well as those containing small amounts of other elements, such as manganese, zinc or barium. Specific examples of iron oxide include ferrites and magnetites. In addition, the magnetic-responsive particle component can be comprised of any of the known alloys of iron, such as those containing aluminum, silicon, cobalt, nickel, vanadium, molybdenum, chromium, tungsten, manganese and/or copper.

The magnetic-responsive particle component can also be comprised of the specific iron-cobalt and iron-nickel alloys described in U.S. Pat. No. 5,382,373. The iron-cobalt alloys useful in the invention have an iron:cobalt ratio ranging from about 30:70 to 95:5, preferably ranging from about 50:50 to 85:15, while the iron-nickel alloys have an iron:nickel ratio ranging from about 90:10 to 99:1, preferably ranging from about 94:6 to 97:3. The iron alloys may contain a small amount of other elements, such as vanadium, chromium, etc., in order to improve the ductility and mechanical properties of the alloys. These other elements are typically present in an amount that is less than about 3.0% by weight. Due to their ability to generate somewhat higher yield stresses, the iron-cobalt alloys are presently preferred over the iron-nickel alloys for utilization as the particle component in a magnetorheological material. Examples of the preferred iron-cobalt alloys can be commercially obtained under the tradenames HYPERCO (Carpenter Technology), HYPERM (F. Krupp Widiafabrik), SUPERMENDUR (Arnold Eng.) and 2V-PERMENDUR (Western Electric).

The magnetic-responsive particle component of the invention is typically in the form of a metal powder which can be prepared by processes well known to those skilled in the art. Typical methods for the preparation of metal powders include the reduction of metal oxides, grinding or attrition, electrolytic deposition, metal carbonyl decomposition, rapid solidification, or smelt processing. Various metal powders that are commercially available include straight iron powders, reduced iron powders, insulated reduced iron powders, cobalt powders, and various alloy powders such as 48%!Fe/ 50%!Co/ 2%!V powder available from UltraFine Powder Technologies.

The preferred magnetic-responsive particles are those that contain a majority amount of iron in some form. Carbonyl iron powders that are high purity iron particles made by the thermal decomposition of iron pentacarbonyl are particularly preferred. Carbonyl iron of the preferred form is commercially available from ISP Technologies, GAF Corporation and BASF Corporation.

The particle size should be selected so that it exhibits multi-domain characteristics when subjected to a magnetic field. The magnetic-responsive particles should have an average particle size distribution of at least about 0.1 μm, preferably at least about 1 μm. The average particle size distribution should range from about 0.1 to about 500 μm, with from about 1 to about 500 μm being preferred, about 1 to about 250 μm being particularly preferred, and from about 1 to about 100 μm being especially preferred.

The amount of magnetic-responsive particles in the magnetorheological fluid depends upon the desired magnetic activity and viscosity of the fluid, but should be from about 5 to about 50, preferably from about 15 to 40, percent by volume based on the total volume of the magnetorheological fluid.

The carrier component is a fluid that forms the continuous phase of the magnetorheological fluid. Suitable carrier fluids may be found to exist in any of the classes of oils or liquids known to be carrier fluids for magnetorheological fluids such as natural fatty oils, mineral oils, polyphenylethers, dibasic acid esters, neopentylpolyol esters, phosphate esters, polyesters (such as perfluorinated polyesters), synthetic cycloparaffin oils and synthetic paraffin oils, unsaturated hydrocarbon oils, monobasic acid esters, glycol esters and ethers, synthetic hydrocarbon oils, perfluorinated polyethers, and halogenated hydrocarbons, as well as mixtures and derivatives thereof. The carrier component may be a mixture of any of these classes of fluids. The preferred carrier component is non-volatile, non-polar and does not include any significant amount of water. The carrier component (and thus the magnetorheological fluid) particularly preferably should not include any volatile solvents commonly used in lacquers or compositions that are coated onto a surface and then dried such as toluene, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, and acetone. Descriptions of suitable carrier fluids can be found, for example, in U.S. Pat. No. 2,751,352 and U.S. Pat. No. 5,382,373, both hereby incorporated by reference. Hydrocarbons, such as mineral oils, paraffins, cycloparaffins (also known as naphthenic oils) and synthetic hydrocarbons are the preferred classes of carrier fluids. The synthetic hydrocarbon oils include those oils derived from oligomerization of olefins such as polybutenes and oils derived from high alpha olefins of from 8 to 20 carbon atoms by acid catalyzed dimerization and by oligomerization using trialuminum alkyls as catalysts. Such poly-α-olefin oils are particularly preferred carrier fluids. Carrier fluids appropriate to the present invention may be prepared by methods well known in the art and many are commercially available.

The carrier fluid of the present invention is typically utilized in an amount ranging from about 50 to 95, preferably from about 60 to 85, percent by volume of the total magnetorheological fluid.

The magnetorheological fluid can optionally include other additives such as a thixotropic agent, a carboxylate soap, an antioxidant, a lubricant and a viscosity modifier. If present, the amount of these optional additives typically ranges from about 0.25 to about 10, preferably about 0.5 to about 7.5, volume percent based on the total volume of the magnetorheological fluid.

Useful thixotropic agents are described, for example, in WO 94/10693 and commonly-assigned U.S. patent application Ser. No. 08/575,240, incorporated herein by reference. Such thixotropic agents include polymer-modified metal oxides. The polymer-modified metal oxide can be prepared by reacting a metal oxide powder with a polymeric compound that is compatible with the carrier fluid and capable of shielding substantially all of the hydrogen-bonding sites or groups on the surface of the metal oxide from any interaction with other molecules. Illustrative metal oxide powders include precipitated silica gel, fumed or pyrogenic silica, silica gel, titanium dioxide, and iron oxides such as ferrites or magnetites. Examples of polymeric compounds useful in forming the polymer-modified metal oxides include siloxane oligomers, mineral oils and paraffin oils, with siloxane oligomers being preferred. The metal oxide powder may be surface-treated with the polymeric compound through techniques well known to those skilled in the art of surface chemistry. A polymer-modified metal oxide, in the form of fumed silica treated with a siloxane oligomer, can be commercially obtained under the trade names AEROSIL R-202 and CABOSIL TS-720 from DeGussa Corporation and Cabot Corporation, respectively.

Examples of the carboxylate soap include lithium stearate, calcium stearate, aluminum stearate, ferrous oleate, ferrous naphthenate, zinc stearate, sodium stearate, strontium stearate and mixtures thereof.

The viscosity of the magnetorheological fluid is dependent upon the specific use of the magnetorheological fluid. In the instance of a magnetorheological fluid that is used with a damper the carrier fluid should have a viscosity of 6 to 500, preferably 15 to 395, Pa-sec measured at 40° C. in the off-state.

The magnetorheological fluid can be used in any controllable device such as dampers, mounts, clutches, brakes, valves and similar devices. These magnetorheological devices include a housing or chamber that contains the magnetorheological fluid. Such devices are known and are described, for example, in U.S. Pat. No. 5,277,281; U.S. Pat. No. 5,284,330; U.S. Pat. No. 5,398,917; U.S. Pat. Nos. 5,492,312; 5,176,368; 5,257,681; 5,353,839; and 5,460,585, all incorporated herein by reference, and PCT published patent application WO 96/07836. The fluid is particularly suitable for use in devices that require exceptional durability such as dampers. As used herein, "damper" means an apparatus for damping motion between two relatively movable members. Dampers include, but are not limited to, shock absorbers such as automotive shock absorbers. The magnetorheological dampers described in U.S. Pat. No. 5,277,281 and U.S. Pat. No. 5,284,330, both incorporated herein by reference, are illustrative of magnetorheological dampers that could use the magnetorheological fluid.

Examples of the magnetorheological fluid were prepared as follows:

A synthetic hydrocarbon oil derived from poly-α-olefin (available from Albemarle Corp. under the tradename DURASYN 164) was homogeneously mixed with the additives and in the amounts shown in Table 1. To this homogeneous mixture, carbonyl iron (available from GAF Corp. under the tradename R2430) in the amount shown in Table 1 was added while continuing mixing. Fumed silica (available from Cabot Corp. under the tradename CAB-O-SIL TS-720) in the amount shown in Table 1 was then added while continuing mixing. The full formulation then was mixed while cooling with an ice bath to maintain the temperature near ambient. Table 1 shows the composition of the fluids prepared with all quantities in weight percent based on the total weight of the final fluid. In all the fluids the carrier fluid (DURASYN 164) was 70.2 volume %, the carbonyl iron was 25 volume % and the CAB-O-SIL TS-720 was 1.8 volume %.

                                  TABLE 1__________________________________________________________________________            Non-metal                    Zinc   Antimony    Organo-     Amine- dialkyl-                    diamyldithio-                           dialkyl-    molybdenum     alkylphosphate            dithiophosphate                    carbamate                           dithiophosphateSample    Molyvan 855     Vanlube 9123            Vanlube 7611M                    Vanlube AZ                           Vanluble 622__________________________________________________________________________Fluid 1    0     0      3.0     0      0Fluid 2    1.5   0      1.5     0      0Fluid 3    0     0      0       2.51                           0.5Fluid 4    0.5   0      0       2.0    0.5Fluid 5    1.0   0      0       1.51                           0.5Fluid 6    0     0      0       3.0    0__________________________________________________________________________ 1 An antimony dialkylthiocarbamate (Vanlube ® 73 available from R. T. Vanderbuilt) was substituted for the zinc diamyldithiocarbamate.
Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2751352 *23 Aug 195119 Jun 1956Shell DevMagnetic fluids
US2805997 *29 Jun 195510 Sep 1957California Research CorpLubricant composition
US2886151 *7 Jan 194912 May 1959Wefco IncField responsive fluid couplings
US4063000 *17 Sep 197513 Dec 1977Fuji Photo Film Co., Ltd.Process for production of ferromagnetic powder
US4164473 *28 Jul 197814 Aug 1979Exxon Research & Engineering Co.Organo molybdenum friction reducing antiwear additives
US4253886 *8 Aug 19773 Mar 1981Fuji Photo Film Co., Ltd.Corrosion resistant ferromagnetic metal powders and method of preparing the same
US4834898 *14 Mar 198830 May 1989Board Of Control Of Michigan Technological UniversitySurfactants
US4889647 *14 Nov 198526 Dec 1989R. T. Vanderbilt Company, Inc.Organic molybdenum complexes
US4990271 *7 Sep 19895 Feb 1991Exxon Research And Engineering CompanyAntiwear, antioxidant and friction reducing additive for lubricating oils
US5043070 *13 Nov 198927 Aug 1991Board Of Control Of Michigan Technological UniversityMagnetic solvent extraction
US5094769 *13 May 198810 Mar 1992International Business Machines CorporationMineral oil or poly alpha olefin oil, filler, coupler
US5137647 *9 Dec 199111 Aug 1992R. T. Vanderbilt Company, Inc.Organic molybdenum complexes
US5143637 *15 Feb 19911 Sep 1992Nippon Seiko Kabushiki KaishaHeat resistance, water resistance, low viscosity
US5213704 *13 Sep 199125 May 1993International Business Machines CorporationProcess for making a compliant thermally conductive compound
US5271858 *2 Oct 199221 Dec 1993Ensci Inc.Field dependent fluids containing electrically conductive tin oxide coated materials
US5382373 *30 Oct 199217 Jan 1995Lord CorporationMagnetorheological materials based on alloy particles
US5412130 *8 Jun 19942 May 1995R. T. Vanderbilt Company, Inc.Method for preparation of organic molybdenum compounds
WO1994010692A1 *12 Oct 199311 May 1994Lord CorpLow viscosity magnetorheological materials
WO1994010693A1 *18 Oct 199311 May 1994Lord CorpThixotropic magnetorheological materials
WO1994010694A1 *27 Oct 199311 May 1994Lord CorpMagnetorheological materials utilizing surface-modified particles
Non-Patent Citations
Reference
1"Vanderbilt Lubricant Additives" R.T. Vanderbilt Company, Inc.; Technical Bulletin No. 941; Jun. 1994.
2 *(Derwent Abstract) DD A 296574 Jul. 4, 1990.
3(Derwent Abstract) DD A -296574 Jul. 4, 1990.
4 *Japan (Derwent Abstract) JP A 62 195729 Aug. 28, 1987.
5Japan (Derwent Abstract) JP A -62-195729 Aug. 28, 1987.
6 *Japan JP B 89 021202 Apr. 20, 1989.
7Japan JP B -89-021202 Apr. 20, 1989.
8 *Vanderbilt Lubricant Additives R.T. Vanderbilt Company, Inc.; Technical Bulletin No. 941; Jun. 1994.
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US616863425 Mar 19992 Jan 2001Geoffrey W. SchmitzHydraulically energized magnetorheological replicant muscle tissue and a system and a method for using and controlling same
US62340608 Mar 199922 May 2001Lord CorporationControllable pneumatic apparatus including a rotary-acting brake with field responsive medium and control method therefor
US63022498 Mar 199916 Oct 2001Lord CorporationLinear-acting controllable pneumatic actuator and motion control apparatus including a field responsive medium and control method therefor
US63951933 May 200028 May 2002Lord CorporationMagnetorheological compositions
US64754043 May 20005 Nov 2002Lord CorporationInstant magnetorheological fluid mix
US652797220 Feb 20014 Mar 2003The Board Of Regents Of The University And Community College System Of NevadaMagnetorheological polymer gels
US654798314 Dec 200015 Apr 2003Delphi Technologies, Inc.Durable magnetorheological fluid compositions
US659943914 Dec 200029 Jul 2003Delphi Technologies, Inc.Hard magnetizable particles having hardness greater than B50 on the Rockwell scale, carrier fluid consisting of polyalphaolefin and a plasticizer, untreated fumed silica
US663844321 Sep 200128 Oct 2003Delphi Technologies, Inc.Comprises mixture of 1-dodecene polyalphaolefin and a diester such as dioctyl sebacate (produces seal swelling and lowers the pour point); improved viscosity and low temperature flow, low volatility
US676452022 Jan 200120 Jul 2004Massachusetts Institute Of TechnologyElectronically controlled prosthetic knee
US681814329 Jan 200316 Nov 2004Delphi Technologies, Inc.Durable magnetorheological fluid
US687155328 Mar 200329 Mar 2005Delphi Technologies, Inc.Integrating fluxgate for magnetostrictive torque sensors
US68724277 Feb 200329 Mar 2005Delphi Technologies, Inc.Method for producing electrical contacts using selective melting and a low pressure kinetic spray process
US6881353 *15 Sep 200319 Apr 2005General Motors CorporationMagnetorheological fluids with stearate and thiophosphate additives
US6886819 *6 Nov 20023 May 2005Lord CorporationMR fluid for increasing the output of a magnetorheological fluid damper
US69242492 Oct 20022 Aug 2005Delphi Technologies, Inc.Direct application of catalysts to substrates via a thermal spray process for treatment of the atmosphere
US694930016 Apr 200327 Sep 2005Delphi Technologies, Inc.Product and method of brazing using kinetic sprayed coatings
US70016711 Oct 200321 Feb 2006Delphi Technologies, Inc.Kinetic sprayed electrical contacts on conductive substrates
US702494623 Jan 200411 Apr 2006Delphi Technologies, Inc.Assembly for measuring movement of and a torque applied to a shaft
US707070723 May 20024 Jul 2006Lord CorporationUseful in devices or systems for controlling vibration and/or noise; performance; for controlling damping in various devices, such as dampers, shock absorbers, and elastomeric mounts
US707070830 Apr 20044 Jul 2006Delphi Technologies, Inc.Magnetorheological fluid resistant to settling in natural rubber devices
US710148725 Nov 20035 Sep 2006Ossur Engineering, Inc.Magnetorheological fluid compositions and prosthetic knees utilizing same
US71088939 Jul 200319 Sep 2006Delphi Technologies, Inc.Providing two populations of particles; providing a supersonic nozzle; directing a flow of a gas through the nozzle, maintaining the gas at a selected temperature, and injecting particles into the nozzle; forming a coating on the substrate
US71980716 May 20053 Apr 2007Össur Engineering, Inc.Systems and methods of loading fluid in a prosthetic knee
US719813729 Jul 20043 Apr 2007Immersion CorporationSystems and methods for providing haptic feedback with position sensing
US72173721 Nov 200215 May 2007Lord CorporationMagnetorheological composition
US727900922 Aug 20039 Oct 2007Massachusetts Institute Of TechnologySpeed-adaptive and patient-adaptive prosthetic knee
US733523315 Mar 200626 Feb 2008Ossur HfMagnetorheological fluid compositions and prosthetic knees utilizing same
US733534130 Oct 200326 Feb 2008Delphi Technologies, Inc.Stacks are formed by applying a band of a kinetic spray electroconductive material, comprises copper, copper alloy, nickel, nickel alloy, aluminum, aluminum alloy, stainless steel, and mixtures; without the need for glues or other adhesives
US73514502 Oct 20031 Apr 2008Delphi Technologies, Inc.Correcting defective kinetically sprayed surfaces
US744509411 Oct 20054 Nov 2008The United States Of America As Represented By The Secretary Of The Air ForcePassive magneto-rheological vibration isolation apparatus
US74556966 May 200525 Nov 2008össur hfDynamic seals for a prosthetic knee
US747583123 Jan 200413 Jan 2009Delphi Technologies, Inc.Modified high efficiency kinetic spray nozzle
US747642223 May 200213 Jan 2009Delphi Technologies, Inc.Copper circuit formed by kinetic spray
US75110844 Feb 200331 Mar 2009Basf AktiengesellschaftPhotoinitiators; phosphine oxide structure with hydroxylamino, alkoxylamino, or hydrazido groups on the central phosphorus atom; simple synthesis; high tolerance to functional groups, very low tendency to migrate; photographic materials, radiation curing of photopolymerizable coatings, inks, dispersions
US752215227 May 200421 Apr 2009Immersion CorporationProducts and processes for providing haptic feedback in resistive interface devices
US755614015 Aug 20077 Jul 2009Martin Engineering CompanyBulk material handling system
US75672431 Jun 200428 Jul 2009Immersion CorporationSystem and method for low power haptic feedback
US757569517 Jan 200718 Aug 2009Delphi Technologies, Inc.Organomolybdenum dithiocarbamate, ashless dithiocarbamate, aminic antioxidant, and triazole compound
US762825419 Sep 20088 Dec 2009The United States Of America As Represented By The Secretary Of The Air ForcePassive magneto-rheological vibration isolation apparatus using a shielding sleeve
US766970815 Aug 20072 Mar 2010Martin Engineering CompanyBulk material handling system and control
US767407614 Jul 20069 Mar 2010F. W. Gartner Thermal Spraying, Ltd.Feeder apparatus for controlled supply of feedstock
US76911546 May 20056 Apr 2010össur hfSystems and methods of controlling pressure within a prosthetic knee
US77401263 Dec 200822 Jun 2010Martin Engineering CompanyBulk material handling system
US77401273 Dec 200822 Jun 2010Martin Engineering CompanyBulk material handling system
US776426824 Sep 200427 Jul 2010Immersion CorporationSystems and methods for providing a haptic device
US77753413 Dec 200817 Aug 2010Martin Engineering CompanyBulk material handling system
US77990918 Oct 200721 Sep 2010Massachusetts Institute Of TechnologyControl system for prosthetic knee
US795982229 Jun 200614 Jun 2011Basf SeMagnetorheological liquid
US800208910 Sep 200423 Aug 2011Immersion CorporationSystems and methods for providing a haptic device
US801384724 Aug 20046 Sep 2011Immersion CorporationMagnetic actuator for providing haptic feedback
US801843426 Jul 201013 Sep 2011Immersion CorporationSystems and methods for providing a haptic device
US80379973 Dec 200818 Oct 2011Martin Engineering CompanyBulk material handling system and control
US80699713 Dec 20086 Dec 2011Martin Engineering CompanyBulk material handling system and control
US815451220 Apr 200910 Apr 2012Immersion CoporationProducts and processes for providing haptic feedback in resistive interface devices
US82057416 Aug 201026 Jun 2012Martin Engineering CompanyMethod of adjusting conveyor belt scrapers and open loop control system for conveyor belt scrapers
US824836324 Oct 200721 Aug 2012Immersion CorporationSystem and method for providing passive haptic feedback
US844143311 Aug 200414 May 2013Immersion CorporationSystems and methods for providing friction in a haptic feedback device
US848629218 Sep 200716 Jul 2013Basf SeMagnetorheological formulation
US861725422 Jan 201031 Dec 2013Ossur HfControl system and method for a prosthetic knee
US861903127 Jul 200931 Dec 2013Immersion CorporationSystem and method for low power haptic feedback
US880379626 Aug 200412 Aug 2014Immersion CorporationProducts and processes for providing haptic feedback in a user interface
USRE3996129 Apr 200325 Dec 2007össur hfComputer controlled hydraulic resistance device for a prosthesis and other apparatus
USRE4290320 Jul 20068 Nov 2011Massachusetts Institute Of TechnologyElectronically controlled prosthetic knee
DE19852152A1 *4 Nov 199818 May 2000Mediport Kardiotechnik GmbhMagnetische Teilchen, magnetische Dispersionen und Verfahren zu ihrer Herstellung
DE19852152C2 *4 Nov 199826 Sep 2002Berlin Heart AgMagnetische Teilchen, deren Herstellung und Verfahren zur Herstellung magnetischer Dispersionen davon
EP1283532A2 *5 Aug 200212 Feb 2003General Motors CorporationMagnetorheological fluids with stearate and thiophosphate additives
EP1423859A1 *3 Sep 20022 Jun 2004Behr America, IncMagnetorheological fluids with an additive package
EP1492133A1 *16 Jun 200429 Dec 2004General Motors CorporationMagnetorheological fluids with stearate and thiophosphate additives
EP1811529A1 *18 Jan 200725 Jul 2007Delphi Technologies, Inc.Additives package and magnetorheological fluid formulations for extended durability
EP1918944A2 *26 Oct 20077 May 2008Repsol Ypf S.A.Magnetorheological Fluid (MRF)
WO2000053936A12 Mar 200014 Sep 2000Lord CorpControllable pneumatic apparatus including a rotary-acting brake with field responsive medium and control method therefor
WO2000053937A12 Mar 200014 Sep 2000Lord CorpLinear-acting controllable pneumatic actuator and motion control apparatus including a field responsive medium and control method therefor
WO2004044931A2 *6 Nov 200327 May 2004Lord CorpImproved mr device
WO2012106597A13 Feb 20129 Aug 2012Lord CorporationPolyols and their use in hydrocarbon lubricating and drilling fluids
Classifications
U.S. Classification252/62.52, 252/62.54
International ClassificationH01F1/44
Cooperative ClassificationH01F1/447
European ClassificationH01F1/44R
Legal Events
DateCodeEventDescription
27 Feb 2009FPAYFee payment
Year of fee payment: 12
25 Apr 2005FPAYFee payment
Year of fee payment: 8
17 Apr 2001FPAYFee payment
Year of fee payment: 4
15 Aug 1996ASAssignment
Owner name: LORD CORPORATION, NORTH CAROLINA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MUNOZ, BETH C.;REEL/FRAME:008091/0079
Effective date: 19960809